linux-kernel - Re: [PATCH] time: Add locking to xtime access in get

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Message-ID: <1304550358.2943.10.camel@work-vm>
Date:	Wed, 04 May 2011 16:05:58 -0700
From:	john stultz <johnstul@...ibm.com>
To:	Max Asbock <masbock@...ux.vnet.ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Anton Blanchard <anton@...ba.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] time: Add locking to xtime access in get_seconds()

On Wed, 2011-05-04 at 09:51 -0700, Max Asbock wrote:
> On Tue, 2011-05-03 at 20:11 -0700, John Stultz wrote:
> > From: John Stultz <johnstul@...ibm.com>
> > 
> > So get_seconds() has always been lock free, with the assumption
> > that accessing a long will be atomic.
> > 
> 
> get_seconds() is used in the x86 machine check handler and there is a
> comment saying:
> /* We hope get_seconds stays lockless */
> 
> This needs to be carefully looked at if locking is introduced to
> get_seconds().

Ah. Thanks for pointing this out Max.

I'll go ahead and use Andi's suggestion of the rmb();

Patch soon to follow.

thanks
-john


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